Electronically controlled high pressure fuel systems are known and commonly used in the automotive and heavy duty truck industries. Such systems typically include a fuel pump operable to provide high pressure fuel to a collection unit that supplies the pressurized fuel to one or more fuel injectors. One or more pressure sensors are typically provided for monitoring and controlling the fuel pressure throughout the system.
An example of one such system is described in U.S. Pat. No. 5,678,521 to Thompson et al., which is assigned to the assignee of the present invention. The Thompson et al. fuel system includes a pair of cam driven high pressure fuel pumps operable to pump fuel from a low pressure fuel source to an accumulator. The accumulator passes the high pressure fuel to a single injection control valve which is electronically controllable to supply the fuel to a distributor unit. The distributor, in turn, distributes the fuel to any of a number of fuel injectors. The accumulator includes a pressure sensor for monitoring accumulator pressure. An electronic control unit monitors accumulator pressure, throttle position and engine speed, and is operable to control the operation of the fuel system in accordance therewith.
High pressure fuel systems of the type just described, while having many advantages over prior mechanical systems, have certain drawbacks associated therewith. For example, while fuel pumping and pressure sensor related faults and failures may be detectable in such systems, no known provisions have been made heretofore for controlling the high pressure pump(s) under such conditions. If left uncontrolled, overpumping and/or overfueling could occur which, in the extreme, could result in fuel system and/or engine damage, and one common technique for addressing such failures is to shut the engine down. However, while this approach avoids potential damage to the engine and/or components, it unnecessarily strands both the vehicle and occupant(s).
What is therefore needed in an electrically controlled high pressure fuel system are techniques for controlling the one or more high pressure fuel pumps and fuel injection strategies under failure conditions associated with the fuel pump and pressure sensor to avoid unnecessary engine shut down. Such techniques should ideally direct the fuel control system to enter limp home fueling modes in response to either pressure sensor or fuel pumping related failure conditions.